/*
题目：https://leetcode.cn/problems/longest-palindromic-subsequence/
区间dp:在区间上dp,递归法，三要素：方程，初始化，打表
*/
class Solution {
public:
    int longestPalindromeSubseq(string s) {
        int n = s.size();
        vector<vector<int>>dp(n,vector<int>(n));
        for(int i = n -1; i >=0; i--){
            dp[i][i] = 1;
            char c1 = s[i];
            for(int j = i + 1; j < n; j++){
                char c2 = s[j];
                if(c1==c2){
                    dp[i][j] = dp[i+1][j-1] +  2;
                }
                else{
                    dp[i][j] = max(dp[i+1][j],dp[i][j-1]);
                }
            }
        }
        return dp[0][n-1];
    }
};